A large percentage of agricultural work vehicles are supported and propelled by four or more wheels on front and rear axles. In work conditions requiring low ground pressure and increased traction, as many as four additional wheels are added to the conventional four wheels. As an alternative to the four wheel agricultural vehicles, self-laying track-type work vehicles are often employed because they offer excellent traction and low ground pressure. Work vehicles having either metal chain track or elastomeric belt track are available. Although track-type work vehicles offer many advantages over wheel type vehicles, sharp turning of the track-type vehicles can disturb soil and vegetation. This is due to the large amount of ground contact offered by the track assemblies, such ground contact causing a shearing action during turning operations.
One type of a vehicle having a track structure and steerable wheels is disclosed in U.S. Pat. No. 1,455,906 issued to W. C. Cox on May 22, 1923. In this patent a motor vehicle is equipped with an endless track structure at the rear of the vehicle and conventional steerable wheels at the front of the vehicle. Cushioning means are provided in the track sections to cushion the movement of the vehicle wheels upon their respective tracks. A hand wheel is disposed in proximity to the seat of the drive to adjust the tracks.
Another type of traction apparatus is disclosed in U.S. Pat. No. 2,057,211, issued to A. T. Shere on Oct. 13, 1936. This patent discloses a track-laying type tractor having track-type structure at the rear and wheels at the front. Various other modifications are disclosed for converting an automobile into a crawler type tractor. This particular type of conversion would appear impractical in view of the different design requirements between automobiles and tractors.
The present invention is directed toward overcoming one or more of the problems as set forth above.